Triggering circuit of the overvoltage protection

ABSTRACT

The design of the triggering circuit  1  of the overvoltage protection, connected via three poles  4  to the spark gap of the overvoltage protection, provided with the first input terminal  2  and the second main terminal  3 , whose principle consists that an auxiliary electrode  7  of the spark gap  4  is connected in series to the first varistor  8  and one end of the secondary winding  14  of the transformer  13 , the other end of which is connected to the second main electrode  6  of the spark gap  4  and the second input terminal  3 , whereas one end of the primary winding  15  of the transformer  13  is connected in series to the gas discharge tube  10 , the second varistor  9 , resistor  11  and capacitor  12 , connected to the other end of the primary winding  15  of the transformer  13 , connected to the second input terminal  3 , whereas the junction connecting the second varistor  9  to the resistor  11  is interconnected with the junction, connecting the first input terminal  2  to the first main electrode  5  of the spark gap  4.    
     The advantage of such a design of the triggering circuit  1  of overvoltage protection resides in the thermosensitive disconnector  17  coupled with the thermal coupling  16  to the second varistor  9 , is either connected in series to the second varistor  9 , or connected to the link of the junction connecting the second varistor  9  to the resistor  11  and the junction connecting the first input terminal  2  to the first main electrode  5  of the spark gap  4 , or that the thermosensitive disconnector  17  is connected between the primary winding  15  of the transformer  13  and the gas discharge tube  10.

TECHNOLOGICAL BACKGROUND

This invention relates to the design of the triggering circuit of the overvoltage protection, representing electrical protection circuits designed to reduce overvoltage in a protected distribution system. The overvoltage protection comprises the spark gap of the overvoltage protection provided with the first input terminal, the second input terminal, interconnected in three poles with the triggering circuit of the overvoltage protection.

CURRENT STATE OF TECHNOLOGY

The known technical solutions of triggering circuit designs of overvoltage protection devices deal with the excitation of the transformer primary winding directly by is activating a gas discharge tube with an overvoltage impulse. This design is simple, however, its correct functioning depends on the overvoltage pulse rise and so, in unfavorable circumstances, that is, if the rise of the pulse is low, i.e. the ratio of the voltage derivation to the time derivation is low, the auxiliary electrode of the spark gap will not activate and the discharge between the first main electrode and the second main electrode of the spark gap will not spark, which is the reason why the concept of overvoltage protection is not functional.

This shortcoming is partially resolved by other used designs of the triggering circuit of overvoltage protection comprising a capacitive divider and a gas discharge tube. An example of a more complicated design with a capacitive divider is document GB1076679 “Improvements in Triggered Spark Gap Type Surge Arresters for D.C. Circuits”; a more simplified design is shown in document U.S. Pat. No. 6,111,740 “Overvoltage protection system and overvoltage protection element for an overvoltage protection system”. The disadvantage of these designs is the oscillation character of the current flowing through the triggering circuit of the overvoltage protection. With the oscillation current flowing through the secondary winding of the transformer going through zero, the discharge can extinguish between one of the first main electrode or the second main electrode and the auxiliary electrode of the spark gap; whereas in such case the discharge between the first main electrode and the second main electrode of the spark gap will not be activated, which results in the absence of the protection function of the overvoltage protection. Instead of the capacitive divider, a divider with is semi-conductor voltage limiting components is also used, e.g. in document U.S. Pat. No. 4,683,514 “Surge voltage protective circuit arrangements”.

Another known design of the triggering circuit of overvoltage protection, shown in document FR2902579 “Electrical installation protection device i.e. surge suppressor, has a triggering unit passing spark gaps from the blocking state, in which gaps oppose the current circulation, to the passing state, in which gaps permit fault current to flow in branches”, or the one shown in document US2003/0007303 [U.S. Pat. No. 6,788,519] “Pressure-resistant encapsulated air-gap arrangement for the draining off of damaging perturbances due to overvoltages”, deal with the above-mentioned drawbacks by using a combined divider with a varistor and capacitor. This design of the triggering circuit of overvoltage protection eliminates in some respect the disadvantages of the previous designs, however, the oscillation character of the current flowing through the triggering circuit of the overvoltage protection still remains, and consequently the problem with possible discharge extinguishing between the first main electrode and the second main electrode of the spark gap, which results in the absence of the protective function of the overvoltage protection.

BASIS OF THE INVENTION

The above-described disadvantages are eliminated to a large extent by the design of the triggering circuit of the overvoltage protection, connected in three poles to the spark gap of the overvoltage protection, provided with the first input terminal and the second main terminal, whose principle consists in the case where an auxiliary electrode of the spark gap is connected in series to the first varistor and one end of the is secondary winding of the transformer, the other end of which is connected to the second main electrode of the spark gap and the second input terminal, whereas one end of the primary winding of the transformer is connected in series to the gas discharge tube, the second varistor, resistor and capacitor, connected to the other end of the primary winding of the transformer, connected to the second input terminal, whereas the junction connecting the second varistor to the resistor is interconnected with the junction, connecting the first input terminal to the first main electrode of the spark gap.

The overvoltage protection comprises a spark gap equipped with the first main electrode, the second main electrode, and one auxiliary electrode in order to make the breakdown between the first main electrode and the second main electrode easier, for which the design of the triggering circuit of the overvoltage protection is specified.

The advantages of such a design of the triggering circuit of overvoltage protection offer better triggering ability due to the functioning part of the design of the triggering circuit of the overvoltage protection, located on the primary side of the transformer.

To ensure the design of the overvoltage protection triggering circuit works safely, it is advantageous that the thermosensitive disconnector coupled with the thermal coupling to the second varistor, is either connected in series to the second varistor, or connected to the link of the junction connecting the second varistor to the resistor and the junction connecting the first input terminal to the first main electrode of the spark gap, or that the thermosensitive disconnector is connected between the primary winding of the transformer and the gas discharge tube.

The mentioned advantageous design of the triggering circuit of the overvoltage protection, extended with a thermosensitive disconnector, enables disconnection of the triggering circuit of the overvoltage protection from the protected distribution system in the event of thermal overloading and impermissible heating or overheating of the second varistor, and it prevents it being damaged or subsequent damage that could arise as a result of damage to the whole overvoltage protection.

DRAWING EXPLANATION

The invention will be more closely explained by using drawings, in which

FIG. 1 shows the block diagram of the spark gap of the overvoltage protection, provided with the first input terminal and the second main terminal, connected in three poles to the triggering circuit.

FIG. 2 shows the principal diagram of the spark gap of the overvoltage protection and triggering circuit.

FIG. 3 shows the principal diagram of the spark gap of the overvoltage protection and triggering circuit equipped with a thermosensitive disconnector which is coupled with the thermal coupling to the second varistor and, at the same time, connected between the second varistor and the junction connecting the first input terminal to the resistor.

FIG. 4 shows the principal diagram of the spark gap of the overvoltage protection and the triggering circuit equipped with a thermosensitive disconnector coupled with the thermal coupling to the second varistor and, at the same time, connected between the gas discharge tube and the second varistor.

FIG. 5 shows the principal diagram of the spark gap of the overvoltage protection and triggering circuit equipped with a thermosensitive disconnector coupled with the thermal coupling to the second varistor and, at the same time, connected to the link between the junction connecting the second varistor to the resistor and the junction connecting the first input terminal to the first main electrode of the spark gap.

FIG. 6 shows the principal diagram of the spark gap of the overvoltage protection and the triggering circuit equipped with a thermosensitive disconnector coupled with the thermal coupling to the second varistor and, at the same time, connected between the primary winding of the transformer and the gas discharge tube.

EXAMPLES OF THE TECHNICAL INVENTION′S IMPLEMENTATION

The overvoltage protection subject to FIG. 1 comprises a spark gap 4 of the overvoltage protection provided with the first input terminal 2 and the second input terminal 3, connected in three poles to a triggering circuit 1 of the overvoltage protection.

The basic design of the triggering circuit 1 of the overvoltage protection according to FIG. 2 comprises an auxiliary electrode 7 of the spark gap 4 which is connected in series to the first varistor 8 and one end of the secondary winding 14 of the transformer 13, the other end of which is connected to the second main electrode 6 of the spark gap 4 and to the second input terminal 3, whereas one end of the primary winding 15 of the transformer 13 is connected in series to a gas discharge tube 10, the second varistor 9, resistor 11 and capacitor 12, connected to the other end of the primary winding 15 of the transformer 13, connected to the second input terminal 3, whereas the junction connecting the second varistor 9 to the resistor 11 is interconnected with the junction connecting the first input terminal 2 to the first main electrode 5 of the spark gap 4.

The resistance of the resistor 11 is at least double that of the second root of the ratio of inductance of the primary winding 15 of the transformer 13 and capacitor 12 capacity.

The advantageous windings of the triggering circuit 1 of the overvoltage protection are equipped with a thermosensitive disconnector 17 coupled with the thermal coupling 16 to the second varistor 9. In its simplest embodiment, the thermosensitive disconnector 17 can be executed using a thermal fuse.

The advantageous design of the triggering circuit 1 of the overvoltage protection subject to FIG. 3 is equipped with a thermosensitive disconnector 17 coupled with the thermal coupling 16 to the second varistor 9 and, at the same time, interconnected between the second varistor 9 and the junction connecting the first input terminal 2 to the resistor 11.

The advantageous design of the triggering circuit 1 of the overvoltage protection subject to FIG. 4 is equipped with a thermosensitive disconnector 17 coupled with the thermal coupling 16 to the second varistor 9 and, at the same time, interconnected between the gas discharge tube 10 and the second varistor 9.

The advantageous design of the triggering circuit 1 of the overvoltage protection subject to FIG. 5 is equipped with a thermosensitive disconnector 17 coupled with the thermal coupling 16 to the second varistor 9 and, at the same time, connected to the link between the junction connecting the second varistor 9 to the resistor 11 and the junction connecting the first input terminal 2 to the first main electrode 5 of the spark gap 4.

The advantageous design of the triggering circuit 1 of the overvoltage protection subject to FIG. 6 is equipped with a thermosensitive disconnector 17 thermally coupled 16 to the second varistor 9 and, at the same time, interconnected between the primary winding 15 of the transformer 13 and the gas discharge tube 10.

An equivalent function of the design of the triggering circuit 1 of the overvoltage protection occurs in serial layout of the circuit elements of the second varistor 9 and the gas discharge tube 10, and/or the resistor 11 and capacitor 12, in reverse order, than is shown in FIGS. 2 to 6.

APPLICATION IN INDUSTRY

The design of the triggering circuit of the overvoltage protection subject to this invention can be used in all applications where the distribution systems are at risk of overvoltage. Unlike the known designs, this invention shows better triggering ability and thanks to the provided thermosensitive disconnector, further failures resulting from damage to the whole overvoltage protection can be prevented.

LIST OR SYMBOLS

-   1 trigger circuit -   2 input terminal I -   3 input terminal I -   4 spark gap -   5 main electrode I

6 main electrode II

-   7 auxiliary electrode -   8 varistor I -   9 varistor II -   10 gas discharge tube -   11 resistor -   12 capacitor -   13 transformer -   14 secondary winding -   15 primary winding -   16 thermal coupling -   17 thermosensitive disconnector 

1. The design of the triggering circuit 1 of the overvoltage protection connected via three poles to the spark gap 4 of the overvoltage protection, equipped with the first input terminal 2 and the second input terminal 3, characterized by the auxiliary electrode 7 of the spark gap 4, which is connected in series to the first varistor 8 and one end of the secondary winding 14 of the transformer 13, whose other end is connected to the second main electrode 6 of the spark gap 4 and to the second input terminal 3, whereas one end of the primary winding 15 of the transformer 13 is connected in series to the gas discharge tube 10, the second varistor 9, resistor 11 and capacitor 12, connected to the other end of the primary winding 15 of the transformer 13 connected to the second input terminal 3, whereas the junction connecting the second varistor 9 to the resistor 11 is interconnected with the junction, connecting the first input terminal 2 to the first main electrode 5 of the spark gap
 4. 2. The design of the triggering circuit 1 of the overvoltage protection subject to claim 1, wherein a thermosensitive disconnector 17 coupled with the thermal coupling 16 to the second varistor 9, which is either connected in series to the second varistor 9, or is connected to the link between the junction connecting the second varistor 9 to the resistor 11 and the junction connecting the first input terminal 2 to the first main electrode 5 of the spark gap 4, or the thermosensitive disconnector 17 is connected between the primary winding 15 of the transformer 13 and the gas discharge tube
 10. 